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<a name="Preprocessing-Directives"></a>
<h3 class="section">4.13 Preprocessing Directives</h3>

<p>See <a href="../cpp/Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior">Implementation-defined
behavior</a> in <cite>The C Preprocessor</cite>, for details of these aspects of
implementation-defined behavior.
</p>
<ul>
<li> <cite>The locations within <code>#pragma</code> directives where header name
preprocessing tokens are recognized (C11 6.4, C11 6.4.7).</cite>

</li><li> <cite>How sequences in both forms of header names are mapped to headers
or external source file names (C90 6.1.7, C99 and C11 6.4.7).</cite>

</li><li> <cite>Whether the value of a character constant in a constant expression
that controls conditional inclusion matches the value of the same character
constant in the execution character set (C90 6.8.1, C99 and C11 6.10.1).</cite>

</li><li> <cite>Whether the value of a single-character character constant in a
constant expression that controls conditional inclusion may have a
negative value (C90 6.8.1, C99 and C11 6.10.1).</cite>

</li><li> <cite>The places that are searched for an included &lsquo;<samp>&lt;&gt;</samp>&rsquo; delimited
header, and how the places are specified or the header is
identified (C90 6.8.2, C99 and C11 6.10.2).</cite>

</li><li> <cite>How the named source file is searched for in an included &lsquo;<samp>&quot;&quot;</samp>&rsquo;
delimited header (C90 6.8.2, C99 and C11 6.10.2).</cite>

</li><li> <cite>The method by which preprocessing tokens (possibly resulting from
macro expansion) in a <code>#include</code> directive are combined into a header
name (C90 6.8.2, C99 and C11 6.10.2).</cite>

</li><li> <cite>The nesting limit for <code>#include</code> processing (C90 6.8.2, C99
and C11 6.10.2).</cite>

</li><li> <cite>Whether the &lsquo;<samp>#</samp>&rsquo; operator inserts a &lsquo;<samp>\</samp>&rsquo; character before
the &lsquo;<samp>\</samp>&rsquo; character that begins a universal character name in a
character constant or string literal (C99 and C11 6.10.3.2).</cite>

</li><li> <cite>The behavior on each recognized non-<code>STDC #pragma</code>
directive (C90 6.8.6, C99 and C11 6.10.6).</cite>

<p>See <a href="../cpp/Pragmas.html#Pragmas">Pragmas</a> in <cite>The C Preprocessor</cite>, for details of
pragmas accepted by GCC on all targets.  See <a href="Pragmas.html#Pragmas">Pragmas
Accepted by GCC</a>, for details of target-specific pragmas.
</p>
</li><li> <cite>The definitions for <code>__DATE__</code> and <code>__TIME__</code> when
respectively, the date and time of translation are not available (C90
6.8.8, C99 6.10.8, C11 6.10.8.1).</cite>

</li></ul>

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